Multimodal imaging scanners represent one of the main research and development topics in the field of medical diagnostics. The combination of techniques providing correlated functional and anatomical information, increases the accuracy of disease diagnosis, therapymonitoring and assessment. As a matter of fact, they give the possibility to map areas of abnormal molecular activity to the patient-specific anatomy. Physical integration of the imaging systems represents the best solution to achieve consistency in space and time: a simultaneous acquisition reduces clinical examination times and enhances the co-registration, optimizing the quality of the fused images. In this context, the development of integrated SPECT/MRI systems was restrained by the technical constraints related to the mutual compatibility of the scanners. INSERT project, founded by 7th Framework Programme of European Commission, has brought to the development of the first SiPM-based clinical SPECT scanner suitable for insertion inside a commercial MRI. The SPECT INSERT is composed by a static set of 20 gamma cameras organized in a ring shape for a total of 1440 pixels. The clinical instrument was designed for brain imaging, primarily for enhanced stratification of glioma patients prior to patient-specific radio-chemo therapy and for the early assessment of treatment efficacy. INSERT project started six years ago, the scanner has been realized in two versions (preclinical and clinical), and now it is close to its final stages. In the framework of this master thesis, the system was put into operation: the functionality of single gamma cameras composing the SPECT scanner were assessed, solving operating issues, and it was introduced a dual-cooling circuit. The image reconstruction software was optimized for the presence of faulty channels. A particular attention was given to the depth of interaction (DOI) reconstruction, which was analyzed bymeans ofMonte Carlo simulations and through preliminary experimental measurements. Finally, the instrument was calibrated and tested at San RaffaeleHospital, to be evaluated mainly in terms of count-rate, energy and spatial resolution. The discussion is organized into five chapters: the first one concerns the most common multimodality imaging techniques and describes the corresponding advantages and disadvantages. Then, it gives an overview of INSERT project, listing the clinical requirements. The second chapter contains the description of the general components of a gammacamera, focusing on the ones implemented inside INSERT detection modules. The acquisition system and the full architecture of the instrument are also presented. The final part characterizes the cooling strategy. The third chapter describes the reconstruction methods that are used for the planar reconstruction of the projections, showing their pros and cons. The reconstruction of the third coordinate of scintillation is addressed inside the fourth chapter, which provides also preliminary experimental results. The fifth and final chapter concerns the evaluation of the performances of the SPECT scanner, tested as a stand-alone system.
La realizzazione di scanner per imaging multimodale rappresenta uno dei principali argomenti di ricerca e sviluppo nel campo della diagnostica medica. L’integrazione di informazioni funzionali e anatomo-morfologiche permette di aumentare l’accuratezza delle diagnosi, in particolare di quelle precoci, di migliorare il monitoraggio e la valutazione dell’efficacia delle terapie mediche. L’integrazione fisica dei sistemi di imaging, permettendo una scansione simultanea, riduce i tempi di esame e fornisce alle acquisizioni consistenza nel tempo e nello spazio, migliorando la registrazione e di conseguenza la qualità finale delle immagini. In questo ambito, lo sviluppo di sistemi integrati SPECT/MRI è stato frenato da vincoli tecnici relativi alla compatibilità reciproca dei due tipi di scanner. Il progetto INSERT, finanziato dalla Comunità Europea nel contesto del programma FP7- HEALTH, ha portato alla realizzazione del primo scanner SPECT clinico basato su SiPM compatibile con la risonanza magnetica. Lo scanner SPECT è costituito da un insieme di 20 gamma camere disposte ad anello, per un totale di 1440 pixel. Lo strumento clinico è stato progettato per l’imaging cerebrale, con lo scopo principale di migliorare la stratificazione dei pazienti affetti da glioma, facilitando radio e chemioterapia personalizzate. Il progetto è stato avviato sei anni fa, ha previsto lo sviluppo di una versione preclinica e clinica dello strumento, ed ora è vicino alle fasi finali. Nell’ambito di questa tesi di laurea, il sistema clinico è stato messo in funzione, testando imoduli che compongono lo scanner e risolvendone i problemi operativi e introducendo un doppio circuito di raffreddamento. Il software per la ricostruzione dell’immagine è stato ottimizzato per la presenza di canali difettosi e un’attenzione particolare è stata data alla ricostruzione della profondità di interazione (DOI) degli eventi gamma, che è stata analizzata mediante simulazioni Monte Carlo e misure sperimentali preliminari. Infine, lo strumento è stato calibrato e testato presso l’Ospedale San Raffaele, principalmente in termini di count-rate, risoluzione energetica e spaziale. La discussione è stata organizzata in cinque capitoli: il primo introduce le tecniche di imaging multimodale più comuni, descrivendone vantaggi e svantaggi. Inoltre, fornisce una panoramica del progetto INSERT e ne elenca i requisiti clinici. Il secondo capitolo contiene la descrizione delle componenti generali di una gamma camera, e in particolare di quelle implementate nei moduli del sistema INSERT. Inoltre, viene presentato il sistema di acquisizione e l’architettura completa dello strumento. Nella parte finale viene caratterizzata la strategia di raffreddamento. Il terzo capitolo riguarda i metodi di ricostruzione utilizzati per la ricostruzione planare delle proiezioni, e li confronta tra loro. Il quarto capitolo introduce la ricostruzione della terza coordinata di scintillazione e ne mostra i primi risultati sperimentali. Infine, il quinto capitolo riporta la caratterizzazione delle prestazioni dello scanner SPECT, testato come sistema stand-alone.
Characterization and tuning of a clinical MRI-compatible SPECT INSERT
D'ADDA, ILENIA
2018/2019
Abstract
Multimodal imaging scanners represent one of the main research and development topics in the field of medical diagnostics. The combination of techniques providing correlated functional and anatomical information, increases the accuracy of disease diagnosis, therapymonitoring and assessment. As a matter of fact, they give the possibility to map areas of abnormal molecular activity to the patient-specific anatomy. Physical integration of the imaging systems represents the best solution to achieve consistency in space and time: a simultaneous acquisition reduces clinical examination times and enhances the co-registration, optimizing the quality of the fused images. In this context, the development of integrated SPECT/MRI systems was restrained by the technical constraints related to the mutual compatibility of the scanners. INSERT project, founded by 7th Framework Programme of European Commission, has brought to the development of the first SiPM-based clinical SPECT scanner suitable for insertion inside a commercial MRI. The SPECT INSERT is composed by a static set of 20 gamma cameras organized in a ring shape for a total of 1440 pixels. The clinical instrument was designed for brain imaging, primarily for enhanced stratification of glioma patients prior to patient-specific radio-chemo therapy and for the early assessment of treatment efficacy. INSERT project started six years ago, the scanner has been realized in two versions (preclinical and clinical), and now it is close to its final stages. In the framework of this master thesis, the system was put into operation: the functionality of single gamma cameras composing the SPECT scanner were assessed, solving operating issues, and it was introduced a dual-cooling circuit. The image reconstruction software was optimized for the presence of faulty channels. A particular attention was given to the depth of interaction (DOI) reconstruction, which was analyzed bymeans ofMonte Carlo simulations and through preliminary experimental measurements. Finally, the instrument was calibrated and tested at San RaffaeleHospital, to be evaluated mainly in terms of count-rate, energy and spatial resolution. The discussion is organized into five chapters: the first one concerns the most common multimodality imaging techniques and describes the corresponding advantages and disadvantages. Then, it gives an overview of INSERT project, listing the clinical requirements. The second chapter contains the description of the general components of a gammacamera, focusing on the ones implemented inside INSERT detection modules. The acquisition system and the full architecture of the instrument are also presented. The final part characterizes the cooling strategy. The third chapter describes the reconstruction methods that are used for the planar reconstruction of the projections, showing their pros and cons. The reconstruction of the third coordinate of scintillation is addressed inside the fourth chapter, which provides also preliminary experimental results. The fifth and final chapter concerns the evaluation of the performances of the SPECT scanner, tested as a stand-alone system.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/149169